background image

1)

 

SPLIT/SHARED CATHODE 

switch 

2)

 

TONESTACK 

switch 

3)

 

SEND

 ¼” instrument jack 

4)

 

LOOP ON OFF 

switch 

5)

 

RETURN

 ¼” instrument jack 

6)

 

IMPEDANCE SELECTOR

 three-way rotary selector 

7)

 

SPEAKERS

 ¼” speaker jacks (x2)\ 

8)

 

NEGATIVE FEEDBACK (NFB)

 

9)

 

BIAS TEST 

probe jacks (x4) 

10)

 

COM

 probe jack 

11)

 

FULL / HALF 

2-way toggle switch 

12)

 

 HT

 

FUSE

  

13)

 

 MAINS FUSE

 

14)

 

 MAINS

 IEC cable inlet 

 

 

SPLIT/SHARED CATHODE 

switch is to select between the earlier shared cathode 

(330uF/820 ohms) configuration for V1, to the later split cathode (330uF/820 for V1A, and 
0.68uF/2K7ohms for V1B). 
 

TONESTACK 

switch is to select between the earlier 56K slope re 250pF treble 

capacitor, to the later 33K slope re 500pF treble capacitor configs.  

 
 

SEND

 is the Send jack of the effects loop, which is a SOLID STATE BUFFERED type, in 

this amp. A ¼” instrument cable is used, to the Input of your effects.  
 

LOOP ON OFF 

switch is to turn the Buffered Loop on or off.  

 
RETURN

 is the RETURN jack, accepting the Output from your effects, using ¼” instrument 

cable. 
 

IMPEDANCE SELECTOR

 three-way rotary selector.  Set to the position that matches the 

impedance of your speaker cabinet.   
 

NOTE

 – if you are using two speaker cabinets in parallel (ex – two 16 Ohm cabinets), set 

the impedance selector to half that of a single cabinet (in this case, 8 Ohms). 

 

Содержание Plexi 51 All Access

Страница 1: ...50W Amplifier User s Manual...

Страница 2: ...namely from 67 68 69 70 and later 70s as well as the 50W Bass version as well Other than the above we also offer the JTM50 which is the early Plexi circuit but with tube rectification Over the years w...

Страница 3: ...cable from the rear panel MAINS cable inlet to your wall power receptacle 3 Plug the Plexi into your speaker cabinet using 1 4 speaker cable 4 Set the IMPEDANCE SELECTOR to the match the impedance of...

Страница 4: ...witch 3 RECTIFIER 2 way toggle switch 4 INDICATOR LED 5 POST PHASE INVERTER MASTER VOLUME PPIMV control 6 PRESENCE control 7 CHARACTER 2 way toggle switch 8 BASS control 9 BOOST 3 way toggle switch 10...

Страница 5: ...ed by turning the front panel POWER toggle switch to the ON position If INDICATOR does not turn on check your power cable connections and then the fuse on the rear of the unit PRESENCE adjusts the hig...

Страница 6: ...annel You can select none Middle 100pF Right or 1000pF Left VOLUME II adjusts the overall volume and gain of the NORMAL channel of the amp JUMPER is a push pull switch on the VOLUME II control above W...

Страница 7: ...V1B TONESTACK switch is to select between the earlier 56K slope resistor 250pF treble capacitor to the later 33K slope resistor 500pF treble capacitor configs SEND is the Send jack of the effects loop...

Страница 8: ...ower output of the power amp HALF mode configures the power tubes to run in triode operation and this negates any need to reconfigure the IMPEDANCE SELECTOR Please turn the amplifier to STANDBY before...

Страница 9: ...ully follow these steps with the amplifier in OPERATE MASTER at minimum and connected to a speaker load not doing so may damage your amplifier 1 Turn on a digital multimeter DMM and set it to read mil...

Страница 10: ...late dissipation for EL34s 25W and now some math The formula for calculating bias is as follows In most cases amplifiers are biased between 50 and 75 dissipation We bias the the amp to approximately 3...

Страница 11: ...tor inside the amp that changes values when you toggle the Rectifier switch Hence you do not have to rebias for Tube Rectifier operation A FEW COMMENTS ON BIASING Due to the nature of vacuum tube ampl...

Страница 12: ...ed to use a matched and balanced phase inverter It is not necessary Feel free to experiment with different tubes of the same type in your amp though I ve read that the components used in this type of...

Страница 13: ...50 Bass a Bright None To get JTM50 a Rectifier Tube To get 68 Plexi 50 a V1 Cathode Split b V1B Coupler 0 022uF c V2A Cathode Bypass 0 68uF d Tonestack 33K 500pF e Bright Cap 100pF f NFB 47K g Presen...

Страница 14: ...8 Settings templates Please resize and print the templates below to make your settings templates...

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